Pharmacokinetics of fosfluconazole and fluconazole following multiple intravenous administration of fosfluconazole in healthy male volunteers

Antifungal Dosing in Critically Ill Patients on Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is an established advanced life support system, providing temporary cardiac and/or respiratory support in critically ill patients. Fungal infections are associated with increased mortality in patients on ECMO. Antifungal drug dosing for critically ill patients is highly challenging because of altered pharmacokinetics (PK). PK changes during critical illness; in particular, the drug volume of distribution (Vd) and clearance can be exacerbated by ECMO. This article discusses the available literature to inform adequate dosing of antifungals in this patient population. The number of antifungal PK studies in critically ill patients on ECMO is growing; currently available literature consists of case reports and studies with small sample sizes providing inconsistent findings, with scant or no data for some antifungals. Current data are insufficient to provide definitive empirical drug dosing guidance and use of dosing strategies derived from critically patients not on ECMO is reasonable. However, due to high PK variability, therapeutic drug monitoring should be considered where available in critically ill patients receiving ECMO to prevent subtherapeutic or toxic antifungal exposures.

Target- and prodrug-based design for fungal diseases and cancer-associated fungal infections

Invasive fungal infections (IFIs) are emerging as a serious threat to public health and are associated with high incidence and mortality. IFIs also represent a frequent complication in patients with cancer who are undergoing chemotherapy. However, effective and safe antifungal agents remain limited, and the development of severe drug resistance further undermines the efficacy of antifungal therapy. Therefore, there is an urgent need for novel antifungal agents to treat life-threatening fungal diseases, especially those with new mode of action, favorable pharmacokinetic profiles, and anti-resistance activity. In this review, we summarize new antifungal targets and target-based inhibitor design, with a focus on their antifungal activity, selectivity, and mechanism. We also illustrate the prodrug design strategy used to improve the physicochemical and pharmacokinetic profiles of antifungal agents. Dual-targeting antifungal agents offer a new strategy for the treatment of resistant infections and cancer-associated fungal infections.

Asymptomatic pulmonary cryptococcosis presenting with mixed lesions of infiltrative and nodular shadow in an immunocompromised patient

Pulmonary cryptococcosis (PC) is a rare fungal lung infection that usually occurs in immunocompromised hosts. We report a rare case of PC with asymptomatic and mixed lesions of infiltrative and nodular shadows. A woman in her 50s with a 7-year history of methotrexate treatment for rheumatoid arthritis (RA) presented with abnormal chest shadows on annual examination. Chest CT revealed two tiny nodules and two infiltrative shadows in the right lower lobe of the lung. We suspected lung cancer, cryptogenic organising pneumonia or RA-interstitial lung disease. However, transbronchial lung biopsy and positivity for serum cryptococcal antigen confirmed the diagnosis of PC. We initiated treatment with fluconazole, which drastically reduced the chest shadows without any adverse events. Since PC can present with several pulmonary shadows, it should be considered as a differential diagnosis of any pulmonary lesion.

Phosphate moiety in FDA-approved pharmaceutical salts and prodrugs

The salification and prodrug approaches modulate the physicochemical properties and absorption, distribution, metabolism, excretion, and toxicity parameters of drugs and lead candidates. The "phosphate" is one of the key counterions/promoiety used in the salt formation and prodrug synthesis. Salification with phosphoric acid enhances the aqueous solubility and thereby facilitates the administration of a drug by the parenteral route. Phosphate moiety in prodrug synthesis mainly improves permeability by lipophilic substitution. Histamine phosphate is the first phosphate salt, and hydrocortisone phosphate was the first prodrug approved by FDA in 1939 and 1952, respectively. The orange book enlists 12 phosphate salts and 17 phosphate prodrugs. Phosphate prodrugs, namely combretastatin A-4 diphosphate, combretastatin A-4 phosphate, lufotrelvir, TP-1287, pyridoxal phosphate, riboflavin phosphate, and psilocybin are clinical candidates. This review focuses on the FDA-approved phosphate salts and prodrugs from 1939 to 2021. The biopharmaceutical advantage of phosphate salts and prodrugs over the parent molecule is also deliberated.

Augmenting Azoles with Drug Synergy to Expand the Antifungal Toolbox

Fungal infections impact the lives of at least 12 million people every year, killing over 1.5 million. Wide-spread use of fungicides and prophylactic antifungal therapy have driven resistance in many serious fungal pathogens, and there is an urgent need to expand the current antifungal arsenal. Recent research has focused on improving azoles, our most successful class of antifungals, by looking for synergistic interactions with secondary compounds. Synergists can co-operate with azoles by targeting steps in related pathways, or they may act on mechanisms related to resistance such as active efflux or on totally disparate pathways or processes. A variety of sources of potential synergists have been explored, including pre-existing antimicrobials, pharmaceuticals approved for other uses, bioactive natural compounds and phytochemicals, and novel synthetic compounds. Synergy can successfully widen the antifungal spectrum, decrease inhibitory dosages, reduce toxicity, and prevent the development of resistance. This review highlights the diversity of mechanisms that have been exploited for the purposes of azole synergy and demonstrates that synergy remains a promising approach for meeting the urgent need for novel antifungal strategies.

Fluconazole Population Pharmacokinetics after Fosfluconazole Administration and Dosing Optimization in Extremely Low-Birth-Weight Infants

A prospective single-center study was conducted to characterize the pharmacokinetics (PK) of fluconazole (FLCZ) in extremely low-birth-weight infants (ELBWIs) who received fosfluconazole (F-FLCZ). Intravenous F-FLCZ was administered at a dose of 3 mg/kg of body weight every 72 h during the first 2 weeks of life, every 48 h during the third and fourth weeks of life, and every 24 h after 5 weeks of life. Blood samples from ELBWIs treated with F-FLCZ were collected using scavenged samples. The concentration of FLCZ was determined using liquid chromatography-tandem mass spectrometry. The population pharmacokinetic model was established using Phenix NLME 8.2 software. In total, 18 ELBWIs were included in this analysis. Individual PK parameters were determined by a one-compartment analysis with first-order conversion. Postmenstrual age (PMA), serum creatinine (SCr), and alkaline phosphatase were considered covariates for clearance (CL). The mean population CL and the volume of distribution were 0.011 L/h/kg^0.75 and 0.95 L/kg, respectively. Simulation assessments with the final model revealed that the current regimen (3 mg/kg every 72 h) could achieve the proposed target FLCZ trough concentration (>2 μg/mL) in 43.3% and 72.2% of infants with a PMA of ≥37 and 30 to 36 weeks, respectively, and an SCr level of <0.5 mg/dL. Shortened dosing intervals (every 48 or 24 h) might improve the probability of target attainment. This study was the first to assess the PK of F-FLCZ in ELBWI, as well as the first to provide fundamental information about FLCZ exposure after F-FLCZ administration, with the goal of facilitating dose optimization in the ELBWI population.

IMPORTANCE Invasive fungal infection is an important cause of mortality and morbidity in very preterm or very-low-birth-weight infants. In order to limit the risk of invasive fungal infections in this population, the administration of fluconazole is generally recommended for extremely low-birth-weight infants admitted to a neonatal intensive care unit with a Candida species colonization prevalence rate of >10%, under the guidelines of the Infectious Diseases Society of America. Fosfluconazole can reduce the volume of solution required for intravenous therapy compared to fluconazole because it has increased solubility, which is a major advantage for infants undergoing strict fluid management. To date, no study has demonstrated the fluconazole pharmacokinetics after fosfluconazole administration in neonates and infants, and this needs to be clarified. Here, we characterized the pharmacokinetics of fluconazole in extremely low-birth-weight infants who received F-FLCZ and explored the appropriate dosage in this patient population.

Preclinical characterization of an intravenous coronavirus 3CL protease inhibitor for the potential treatment of COVID19

COVID-19 caused by the SARS-CoV-2 virus has become a global pandemic. 3CL protease is a virally encoded protein that is essential across a broad spectrum of coronaviruses with no close human analogs. PF-00835231, a 3CL protease inhibitor, has exhibited potent in vitro antiviral activity against SARS-CoV-2 as a single agent. Here we report, the design and characterization of a phosphate prodrug PF-07304814 to enable the delivery and projected sustained systemic exposure in human of PF-00835231 to inhibit coronavirus family 3CL protease activity with selectivity over human host protease targets. Furthermore, we show that PF-00835231 has additive/synergistic activity in combination with remdesivir. We present the ADME, safety, in vitro, and in vivo antiviral activity data that supports the clinical evaluation of PF-07304814 as a potential COVID-19 treatment.

A preliminary study of the plasma concentrations of orally administered fluconazole in alpacas (Vicugna pacos)

Alpacas residing in the region endemic for Coccidioides spp. are susceptible to serious, disseminated coccidioidomycosis that may result in death. There is currently no oral antifungal dose recommendation for this species. We used a steady-state study design to assess the pharmacokinetics of oral generic fluconazole in alpacas dosed q 24 h for 14 days. Cohorts of 2-3 animals received fluconazole from 6 to 15 mg/kg/day, and pharmacokinetic analysis was performed after each group of animals in order to make dose adjustments for the next group. The final three animals were used as confirmation of our dose recommendation. The median T_max was 7 h, and the median C_max was 1.25 µg/ml per mg/kg dose. The mean dose-normalized 24-h AUC was 41.7 µg h/ml per mg/kg dose (CV = 72%). Based on these results, we recommend alpacas receive a starting dose of oral fluconazole at 10-15 mg/kg/day based on the fluconazole AUC in humans (313-625 µg h/ml). Testing to ascertain putative therapeutic plasma concentrations and monitoring of serum transaminases should be performed.

Discovery of a Novel Inhibitor of Coronavirus 3CL Protease for the Potential Treatment of COVID-19

COVID-19 caused by the SARS-CoV-2 virus has become a global pandemic. 3CL protease is a virally encoded protein that is essential across a broad spectrum of coronaviruses with no close human analogs. The designed phosphate prodrug PF-07304814 is metabolized to PF-00835321 which is a potent inhibitor in vitro of the coronavirus family 3CL pro, with selectivity over human host protease targets. Furthermore, PF-00835231 exhibits potent in vitro antiviral activity against SARS-CoV-2 as a single agent and it is additive/synergistic in combination with remdesivir. We present the ADME, safety, in vitro , and in vivo antiviral activity data that supports the clinical evaluation of this compound as a potential COVID-19 treatment.

Design and Characterization of a Pyridone-Containing EZH2 Inhibitor Phosphate Prodrug

A pyridone-derived phosphate prodrug of an enhancer of zeste homolog 2 (EZH2) inhibitor was designed and synthesized to improve the inhibitor's aqueous solubility. This prodrug (compound 5) was profiled in pharmacokinetic experiments to assess its ability to deliver the corresponding parent compound (compound 2) to animals in vivo following oral administration. Results from these studies showed that the prodrug was efficiently converted to its parent compound in vivo. In separate experiments, the prodrug demonstrated impressive in vivo tumor growth inhibition in a diffuse large B-cell lymphoma Karpas-422 cell line-derived xenograft model. The described prodrug strategy is expected to be generally applicable to poorly soluble pyridone-containing EZH2 inhibitors and provides a new option to enable such compounds to achieve sufficiently high exposures in vivo.

Perpetrator effects of ciclosporin (P-glycoprotein inhibitor) and its combination with fluconazole (CYP3A inhibitor) on the pharmacokinetics of rivaroxaban in healthy volunteers

AIMS

Rivaroxaban exposure is considerably increased by drugs that are combined P-glycoprotein (P-gp) and strong cytochrome P450 (CYP) 3A inhibitors (e.g. ketoconazole). The aim of the present study was to investigate the effects of the potent P-gp inhibitor ciclosporin and its combination with the moderate CYP3A inhibitor fluconazole on rivaroxaban pharmacokinetics and on CYP3A activity.

METHODS

Twelve healthy volunteers received 20 mg rivaroxaban orally alone, in combination with ciclosporin (dose-individualized oral regimen), and in combination with ciclosporin and fluconazole (400 mg day^-1 orally). CYP3A4 activity was estimated using a midazolam microdose. Pharmacokinetics was analysed using noncompartmental and compartmental methods.

RESULTS

Compared to baseline, ciclosporin increased rivaroxaban average exposure by 47% (90% confidence interval 28-68%), maximum concentration by 104% (70-146%), and decreased CYP3A4 activity by 34% (25-42%). Ciclosporin combined with fluconazole increased rivaroxaban average exposure by 86% (58-119%) and maximum concentration by 115% (83-153%), which was considerably stronger than observed in historical controls receiving rivaroxaban with fluconazole alone, and decreased CYP3A4 activity by 79% (76-82%).

CONCLUSION

Patients treated with rivaroxaban in combination with single modulators of multiple elimination pathways or multiple modulators of single elimination pathways (CYP3A, P-gp) require particular care.

Overcoming Clopidogrel Resistance: Three Promising Novel Antiplatelet Drugs Developed in China

Clopidogrel is one of the most frequently prescribed drugs worldwide; however, the presence of clopidogrel resistance and high susceptibility to genetic variations and drug interactions are facilitating the development of other antiplatelet drugs. To overcome clopidogrel resistance, several promising clopidogrel analogues have been developed in China, such as vicagrel (and its deuterated analogues), PLD-301, and W1. These novel chemical analogues are all characterized by much faster and more efficient bioconversion to clopidogrel thiolactone (or 2-oxo-clopidogrel, the precursor of clopidogrel active metabolite) in the intestine than clopidogrel itself through bypassing the first-step P450-mediated oxidation of clopidogrel in the liver. Of them, metabolic conversion of vicagrel and PLD-301 to 2-oxo-clopidogrel is catalyzed by intestinal carboxylesterase 2 and alkaline phosphatase, respectively. In this review article, we summarized all evidence on highly efficient bioconversion to their shared precursor of clopidogrel active metabolite and the mechanisms underlying such a pronounced improvement. These drugs in the pipeline would be promising antiplatelet drugs that could be superior to clopidogrel in future patient care.

In Vivo Microdialysis To Determine Subcutaneous Interstitial Fluid Penetration and Pharmacokinetics of Fluconazole in Intensive Care Unit Patients with Sepsis

The objective of the study was to describe the subcutaneous interstitial fluid (ISF) pharmacokinetics of fluconazole in critically ill patients with sepsis. This prospective observational study was conducted at two tertiary intensive care units in Australia. Serial fluconazole concentrations were measured over 24 h in plasma and subcutaneous ISF using microdialysis. The concentrations in plasma and microdialysate were measured using a validated high-performance liquid chromatography system with electrospray mass spectrometer detector method. Noncompartmental pharmacokinetic analysis was performed. Twelve critically ill patients with sepsis were enrolled. The mean in vivo fluconazole recovery rates ± standard deviation (SD) for microdialysis were 51.4% ± 16.1% with a mean (±SD) fluconazole ISF penetration ratio of 0.52 ± 0.30 (coefficient of variation, 58%). The median free plasma area under the concentration-time curve from 0 to 24 h (AUC0-24) was significantly higher than the median ISF AUC0-24 (340.4 versus 141.1 mg · h/liter; P = 0.004). There was no statistical difference in median fluconazole ISF penetration between patients receiving and not receiving vasopressors (median, 0.28 versus 0.78; P = 0.106). Both minimum and the maximum concentrations of drug in serum (Cmax and Cmin) showed a significant correlation with the fluconazole plasma exposure (Cmax, R(2) = 0.86, P < 0.0001; Cmin, R(2) = 0.75, P < 0.001). Our data suggest that fluconazole was distributed variably, but incompletely, from plasma into subcutaneous interstitial fluid in this cohort of critically ill patients with sepsis. Given the variability of fluconazole interstitial fluid exposures and lack of clinically identifiable factors by which to recognize patients with reduced distribution/exposure, we suggest higher than standard doses to ensure that drug exposure is adequate at the site of infection.

Pharmacokinetic variability and exposures of fluconazole, anidulafungin, and caspofungin in intensive care unit patients: Data from multinational Defining Antibiotic Levels in Intensive care unit (DALI) patients Study

Introduction

The objective of the study was to describe the pharmacokinetics (PK) of fluconazole, anidulafungin, and caspofungin in critically ill patients and to compare with previously published data. We also sought to determine whether contemporary fluconazole doses achieved PK/pharmacodynamic (PD; PK/PD) targets in this cohort of intensive care unit patients.

Methods

The Defining Antibiotic Levels in Intensive care unit patients (DALI) study was a prospective, multicenter point-prevalence PK study. Sixty-eight intensive care units across Europe participated. Inclusion criteria were met by critically ill patients administered fluconazole (n = 15), anidulafungin (n = 9), and caspofungin (n = 7). Three blood samples (peak, mid-dose, and trough) were collected for PK/PD analysis. PK analysis was performed by using a noncompartmental approach.

Results

The mean age, weight, and Acute Physiology and Chronic Health Evaluation (APACHE) II scores of the included patients were 58 years, 84 kg, and 22, respectively. Fluconazole, caspofungin, and anidulafungin showed large interindividual variability in this study. In patients receiving fluconazole, 33% did not attain the PK/PD target, ratio of free drug area under the concentration-time curve from 0 to 24 hours to minimum inhibitory concentration (fAUC_0–24/MIC) ≥100. The fluconazole dose, described in milligrams per kilogram, was found to be significantly associated with achievement of fAUC_0–24/MIC ≥100 (P = 0.0003).

Conclusions

Considerable interindividual variability was observed for fluconazole, anidulafungin, and caspofungin. A large proportion of the patients (33%) receiving fluconazole did not attain the PK/PD target, which might be related to inadequate dosing. For anidulafungin and caspofungin, dose optimization also appears necessary to minimize variability.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0758-3) contains supplementary material, which is available to authorized users.

Fluconazole pharmacokinetics and safety in premature infants

Invasive candidiasis (IC) in the premature infant population is a common infection that results in substantial morbidity and mortality. For these patients, fluconazole is among the first line therapies to treat and prevent IC, and yet few prospective studies investigating its pharmacokinetics (PK) and safety have been performed in this vulnerable population. We review five phase I studies examining the PK of fluconazole in premature infants, which demonstrate markedly differing kinetics compared to adults. Based on these data, a treatment dose of 12 mg/kg/day, with the potential need of a loading dose of 25 mg/kg to achieve rapid steady state concentrations, achieves surrogate pharmacodynamic targets. Additionally, fluconazole appears to be safe to use in this population, with only minimal reversible hepatobiliary effects.

Real-time microscopic observation of Candida biofilm development and effects due to micafungin and fluconazole

To understand the process of Candida biofilm development and the effects of antifungal agents on biofilms, we analyzed real-time data comprising time-lapse images taken at times separated by brief intervals. The growth rate was calculated by measuring the change of biofilm thickness every hour. For the antifungal study, 5-h-old biofilms of Candida albicans were treated with either micafungin (MCFG) or fluconazole (FLCZ). MCFG began to suppress biofilm growth a few minutes after the initiation of the treatment, and this effect was maintained over the course of the observation period. In contrast, the suppressive effects of FLCZ on biofilm growth took longer to manifest: biofilms grew in the first 5 h after treatment, and then their growth was suppressed over the next 10 h, finally producing results similar to those observed with MCFG. MCFG was also involved in the disruption of cells in the biofilms, releasing string-like structures (undefined extracellular component) from the burst hyphae. Thus, MCFG inhibited the detachment of yeast cell clusters from the tips of hyphae. In contrast, FLCZ did not disrupt biofilm cells. MCFG also showed fast antifungal activity against Candida parapsilosis biofilms. In conclusion, our results show that inhibition of glucan synthesis due to MCFG contributed not only to fungicidal activity but also to the immediate suppression of biofilm growth, while FLCZ suppressed growth by inhibiting ergosterol synthesis. Therefore, those characteristic differences should be considered when treating clinical biofilm infections.

Population pharmacokinetics of fluconazole after administration of fosfluconazole and fluconazole in critically ill patients

WHAT IS KNOWN AND OBJECTIVE

Fluconazole is an antifungal agent that is commonly used to treat patients with serious systemic fungal infections in intensive care units. Fosfluconazole is a phosphate prodrug of fluconazole, which was developed to reduce the volume of fluid required to administer fluconazole by intravenous injection. The objective of this study was to characterize the pharmacokinetics of the antifungal fluconazole after the intravenous administration of the prodrug fosfluconazole or fluconazole in critically ill patients with serious systemic fungal infections, by population pharmacokinetic analysis using the nonmem software package.

METHODS

Clinical biochemical data including serum fluconazole levels were obtained from 57 patients treated in the intensive care unit along with two naïve pooled patients gleaned from previous reports. The pharmacokinetic model of fluconazole was estimated using a one-compartment model. The probability that the area under the concentration-time curve is higher than 800 μg h/mL was determined by simulation.

RESULTS

It was assumed that all the administered fosfluconazole was converted to fluconazole with an estimated fosfluconazole-fluconazole conversion rate constant of 2·05/h. The significant covariates for clearance for fluconazole (CL) and volume of distribution for fluconazole (Vd) were resulted in creatinine clearance (CLcr) and body weight (BW), respectively, in the final pharmacokinetic model equations: CL (L/h) = 0·799 × [CLcr (mL/min)/92·7](0·685) and Vd (L) = 48·1 × [BW (kg)/65](1·40) , where the interpatient variabilities in CL and Vd and the intrapatient variability were 44·8%, 79·7% and 19·8%, respectively. On the basis of the results of the Monte Carlo simulation, the probabilities of target attainment were 60%, 26% and 11% for 400 mg/day administration as fluconazole equivalent at CLcr values of 40, 70 and 100 mL/min, respectively.

WHAT IS NEW AND CONCLUSION

The present population pharmacokinetic analysis strongly indicates that fosfluconazole (and fluconazole) dosage should be optimized in terms of CLcr in critically ill patients.

Evaluation of in vitro models for screening alkaline phosphatase-mediated bioconversion of phosphate ester prodrugs

Generating a phosphate prodrug is one of the common approaches for circumventing poor solubility issues of a parent drug. Alkaline phosphatase (ALP) level was determined in rat intestine mucosa scraps, human colon carcinoma (Caco-2) cells, and Madin-Darby canine kidney (MDCK) cells to characterize in vitro models for ALP-mediated phosphate prodrug conversion. In addition, fosphenytoin and fosfluconazole were used as probe prodrugs to evaluate the models. The highest amount of ALP was detected in rat intestinal mucosa scraps, whereas ALP in 5-day cultured MDCK cells was minimal. As anticipated, ALP levels correlated with the parent drug conversion; the shortest cleavage half-life (t(1/2)) was observed in rat mucosa scraps; and MDCK cells showed the slowest conversion. Furthermore, the polarized conversion for the prodrugs was observed in Caco-2 monolayer cells, suggesting the polarized localization of alkaline in differentiated Caco-2 cells. The rate of ALP-mediated conversion was prodrug concentration-dependent with Michaelis-Menten constants of 1160 and 351 microM for fosphenytoin and fosfluconazole, respectively, determined in Caco-2 cells. The results revealed that whereas the intestinal mucosa scraps reserved the highest ALP activities and were shown as a promising in vitro tool for screening the bioconversion of phosphate prodrug, Caco-2 monolayers could provide the predictive information of bioconversion and further offer the capability in characterizing the permeability of prodrug and parent drug.

Epidemiological study of Candida infections in blood: susceptibilities of Candida spp. to antifungal agents, and clinical features associated with the candidemia

The purpose of this study was to evaluate the susceptibility to antifungal agents of Candida spp. isolated from blood samples from patients in our hospital, located in Osaka, Japan. We also examined the clinical background of these patients. We analyzed fungi isolated from clinical blood samples obtained in our hospital over a period of 10 years (1993 to 2002). Antifungal susceptibility testing was carried out for six agents, using the National Committee of Clinical Laboratory Standards (NCCLS) M-27-A2 method. The clinical backgrounds were reviewed using the medical records of 125 patients who were diagnosed as having candidemia. The major fungi isolated were Candida parapsilosis (39.2%) and C. albicans (30.1%), and both were sensitive to fluconazole. One strain of C. glabrata and six strains of C. krusei were resistant to fluconazole, and they constituted 4.4% of all Candida spp. isolated. With the exception of C. parapsilosis, most fungi were susceptible to micafungin, although there is no universally agreed breakpoint for this drug. Analysis of the patients' clinical backgrounds revealed that the major underlying disease was cancer (46.4% excluding hematological malignancies). C. krusei was detected almost exclusively in patients with hematological malignancies. Indwelling venous catheters had been responsible for infection in 93.6% of the infected patients. The clinical outcomes of the 125 patients were favorable in 52% and poor in 48%, and subsequent removal of the indwelling catheters was effective in about half of the patients in whom this was done, with good prognosis. To prevent mycosis and its complications, indwelling catheters should be avoided as much as possible. Attention must be paid to the possibility that resistant isolates of Candida spp. can be selected as a result of the use of antifungal agents.

The effects of hepatic impairment on the pharmacokinetics of fosfluconazole and fluconazole following a single intravenous bolus injection of fosfluconazole

AIMS

Fosfluconazole is a phosphate pro-drug of fluconazole (FLCZ). This study was conducted to determine the pharmacokinetics of fosfluconazole and FLCZ following a single intravenous injection of fosfluconazole in subjects with hepatic impairment and to compare them with healthy subjects.

METHODS

Twenty-four subjects (12 with normal hepatic function and 12 with chronic stable mild to moderate impaired hepatic function) received a single 1000-mg bolus intravenous injection of fosfluconazole. Concentrations of fosfluconazole and FLCZ were determined in plasma and urine samples taken up to 192 h and 48 h postdose, respectively.

RESULTS

The total clearance of fosfluconazole was higher and the t(1/2,Z) and mean residence time were shorter in hepatically impaired subjects than in normal subjects. This may reflect more rapid conversion to FLCZ. The degree of protein binding of fosfluconazole (> 90%) and the amount of fosfluconazole excreted in the urine were similar in both groups. Slightly higher mean plasma concentrations of FLCZ were observed in the impaired group than in the normal group; however, hepatic impairment had no statistically significant effect on the FLCZ pharmacokinetic parameters apart from t(max). The t(max) values were 4.8 h and 3.1 h in the normal and impaired subjects, respectively. The shorter t(max) for FLCZ is also consistent with the more rapid conversion in the impaired subjects. The ratios (95% confidence intervals) for C(max) and AUC of FLCZ (impaired/normal) were 106.0% (92.8, 121.2) and 115.6% (86.4, 154.7), respectively. There were no serious adverse events, and no discontinuations due to adverse events or laboratory test abnormalities. The adverse events reported were mostly mild in severity and no trend could be discerned between the groups.

CONCLUSIONS

Fosfluconazole was more rapidly converted to FLCZ in the hepatically impaired subjects but the FLCZ pharmacokinetic parameters (except t(max)) were not statistically significantly affected by hepatic impairment. Fosfluconazole was well tolerated by both groups. These results suggest that there is no requirement to adjust the dose of fosfluconazole when administered to subjects with mild to moderate hepatic impairment.

The effects of renal impairment on the pharmacokinetics and safety of fosfluconazole and fluconazole following a single intravenous bolus injection of fosfluconazole

AIMS

Fosfluconazole is a phosphate prodrug of fluconazole (FLCZ). This study was conducted to investigate the effect of renal impairment on the pharmacokinetics of fosfluconazole and FLCZ, and to assess the safety and toleration of fosfluconazole following a single intravenous bolus injection of fosfluconazole in subjects with normal and impaired renal function.

METHODS

In an open, parallel-group, two-centre study, subjects with normal and impaired renal function received a single 1000-mg bolus intravenous injection of fosfluconazole. Subjects were categorized as Normal (> 80 ml min(-1)), Mild (51-80 ml min(-1)), Moderate (30-50 ml min(-1)) or Severe (< 30 ml min(-1)) impairment group according to their Cockcroft and Gault creatinine clearance (CLcr) values. Concentrations of fosfluconazole and FLCZ were determined in plasma and urine samples taken up to 240 h and 48 h postdose, respectively.

RESULTS

Fosfluconazole plasma concentrations were very similar across the four groups, and there was no apparent relationship between any of the fosfluconazole pharmacokinetic parameters with increasing renal impairment. The conversion of fosfluconazole to FLCZ was unaffected by the degree of renal impairment. Only small amounts of fosfluconazole were excreted in the urine suggesting almost complete conversion to FLCZ. FLCZ concentrations were still detected in plasma after 240 h postdose and remained higher at the later sampling times in subjects in the Moderate and Severe groups. The area under the plasma concentration vs. time curve between time zero and infinity (AUC), the terminal elimination phase half-life (t(1/2)) and the mean residence time (MRT) of FLCZ all increased with the degree of renal impairment. The ratios (95% confidence interval) for AUC (Renal impairment group/Normal group) were 112.8% (89.5, 142.1), 240.6% (128.2, 451.4) and 355.1% (259.3, 486.3) for the Mild, Moderate and Severe impairment groups, respectively. There was a linear relationship between CLcr with AUC, t(1/2), MRT and the total plasma clearance of FLCZ (CL/F). Both the amount excreted over 48 h in the urine and the renal clearance of FLCZ decreased with an increase in renal impairment. The adverse events reported were mild to moderate in intensity, and there was no observed relationship with impairment group. There were no severe or serious adverse events, and in general fosfluconazole was well tolerated.

CONCLUSIONS

The pharmacokinetics of fosfluconazole, including its efficient conversion into FLCZ, were unaffected by renal impairment. For FLCZ, there was a significant linear relationship between CLcr and AUC, t(1/2), MRT and CL/F, with AUC, t(1/2) and MRT increasing and CL/F decreasing as renal impairment increased. The dose adjustment used for FLCZ (half normal dose for patients with CLcr at <or= 50 ml min(-1)) can be applied to fosfluconazole as well. There were no safety concerns for any subject in this study, and fosfluconazole and FLCZ were well tolerated by all the treatment groups.

[Nonclinical studies and clinical studies on fosfluconazole, a triazole antifungal agent (Prodif)]

Fosfluconazole is a phosphate prodrug of fluconazole that has been developed to reduce the volume of fluid required to administer fluconazole by the intravenous route. Fosfluconazole is hydrolyzed by alkaline phosphatase to fluconazole and phosphoric acid. Fosfluconazole had no significant antifungal activity in vitro. However, in rat models of acute systemic candidiasis and intracranial cryptococcosis, fosfluconazole retained the antifungal potency and efficacy of fluconazole. This reflects the effective conversion of the prodrug to the parent during the course of the experiments. The 2-day-loading dose regimen led to earlier achievement of target fluconazole steady state plasma concentrations compared to use of the 1-day- or no-loading dose regimen of fosfluconazole. The efficacy and safety of fosfluconazole were investigated with the 2-day-loading dose regimen in patients with deep-seated mycosis caused by Candida and Cryptococcus species. The efficacy rates were 73.8% in the domestic Phase III study and 91.7% in the foreign Phase III study. Adverse events were observed in 31 cases (19.4%) out of 160 in both studies. These results indicate that fosfluconazole is effective for the treatment of deep-seated mycosis and shows no clinically significant adverse events in the Phase III studies